Prefabricated and Modular are often used
interchangeably for houses in which the components are built
at a factory, shipped to the building site, and installed.
The main advantage to modular homes is that, once the foundation
has been prepared, the house can "constructed" in
days.

How They’re Made
In a highly engineered manufacturing process, modular homes are built in sections called modules. Once built, the modules undergo a series of quality-control checks in the factory.

After the manufacturing process is complete — typically with interior finish on the floors, walls and ceilings — trucks transport the home to its site, place the modules on a prepared foundation with a crane and join them to the foundation and each other.

While critics have charged that modular homes are too boxy, that refrain is beginning to fade with growing flexibility in design and customization options.